Autism spectrum disorders (ASD) are a neurodevelopmental disorders manifested by a spectrum of behavioral anomalies characterized by impaired social interaction and communication, often accompanied by repetitive and stereotyped behavior. The characteristic impairments may be accompanied by mental retardation and/or epilepsy. The condition becomes apparent within the first 3 years of life and persists into adulthood. In a majority of cases, there is no unequivocally normal period(s) in the child's development (classic autism). Usually, social development is markedly delayed and deviant, and language fails to appear or progress normally. In a smaller group of cases, parents report a period of normal development followed by regression, occasionally abrupt, in the child's language, sociability and play.
The current incidence of autism spectrum disorders is about 1:250 of the total population. The male to female ratio is about 4:1. There has been about a 5-fold increase in the last 10 years in new cases of ASD in the pediatric population of children aged 1.5-6 years. This does not reflect the major increase in newly diagnosed cases prior to 1994 when the diagnostic criteria changed.
There are numerous hypotheses regarding the etiology and pathology of ASD, including a suggested role for immune dysfunction. Autoantibodies against CNS proteins, including neuron-axon filament proteins (NAFP), cerebellar neurofillaments, myelin basic protein (MBP), brain endothelial cells, caudate nucleus, serotonin receptors have been reported in a subset of ASD patients (reviewed in Ashwood and Van de Water, Autoimmun Rev (2004) 3:557-62). There currently exists no genetic or biologic test for diagnosing autism spectrum disorders (ASD). Accordingly there remains a need for understanding the etiology of ASD and for diagnostic tests predictive of an individual's risk for developing the symptoms indicative of an ASD, allowing for early intervention in the treatment of this neurodevelopmental disorder. The present invention fulfills this and other needs.